In recent years, a navigation system uses an application software for retrieving map data from information medium such as DVD-ROM or the like and displaying it on a display unit. In this case, the application software has to be switched depending on a format of the map data provided by the DVD-ROM. For example, when the map data is prepared by using a format 1.0 in a region A and by using a format 2.0 in a region B, different types of application software have to be used respectively in each of the region A and region. B to accommodate the difference of data format. The map data in each of the format 1.0 and format 2.0 is retrieved from the medium such as the DVD-ROM, a HDD or the like and is loaded in a memory under a control of a CPU when a user, or a driver of a vehicle, uses the navigation system. The application software used in the navigation system is also retrieved from the medium to the memory of the navigation system.
The application software executed in, for example, a substrate 1 of the navigation system in FIG. 7A is conventionally determined based on an input of a divided voltage Vd that is applied to a reference input terminal of a CPU 2 after dividing a source voltage Vc by using a series circuit of resistors 3, 4. That is, the CPU 2 determines the application software to be used in the navigation system based on the input of a signal that is derived from A/D conversion of the divided voltage Vd. The input to the CPU 2 may be provided as an ID code from a ROM 5 coupled with the CPU 2 when the navigation system is initialized.
Thus, the conventional navigation system has to have a different product series for respective regions (i.e., for respective data formats) due to above-described operation scheme. That is, the navigation system having the application software designated for each region has to be produced as a different series of products because the application software for a specific region (i.e., for a specific data format) is selected and determined based on a product code of the navigation system. As a result, an increased number of versions of the navigation system leads to a complicated situation such as a version control in a production operation, an inventory operation or the like.
The navigation system disclosed in Japanese patent document JP-A-H10-208194 has an operation scheme that the navigation system in operation determines and switches product specifications based on a current position of the navigation system detected by using map data.
However, the navigation system in the above disclosure suffers from difference of map data format. That is, the navigation system does not work properly when the map data for the current position is provided in a format that is not compatible with the application software used in the navigation system.